1. Field of the Invention
The present invention relates to data filtering, and more particularly, to a signal adaptive filtering method for reducing ringing noise, and a signal adaptive filter suitable for implementing the method. This application for a signal adaptive filtering method and signal adaptive filter for reducing ringing noise is based upon Korean Patent Application No. 97-12498 which is incorporated herein by reference for all purposes.
2. Description of the Related Arts
Generally, picture encoding standards such as MPEG of the International Organization for Standardization (ISO) and H.263 recommended by the International Telecommunication Union (ITU) adopt block-based motion estimation and discrete cosine transform (DCT) of blocks. When an image is highly compressed, the block-based coding may cause a blocking effect and ringing noise. A typical blocking effect is grid noise in a homogeneous area in which adjacent pixels have relatively similar pixel values. Another blocking effect is staircase noise which has the shape of a staircase and is generated along the edge of the image. Also, the ringing noise is due to the typical Gibb's phenomenon which results from the truncation of a DCT coefficient by quantization when the image is highly compressed. The ringing noise causes a problem in that an object in the image is displayed as multiple overlapping objects.